AI will blow my mind when it solves an unsolved mathematical/physics/scientific problem, i.e: "AI, give me a proof for (or against) the Riemann hypothesis"
Actually, it happened _long_ before that - 2018 was when I became aware of this technique, but I'm sure there's previous art: https://nullprogram.com/blog/2018/07/31/ (Prospecting for Hash Functions for those who already know).
That said, this is really brute forcing, not what the OP is asking for, which is providing a novel proof as the response to a prompt (this is instead providing the novel proof as one of thousands of responses, each of which could be graded by a function).
AI will blow my mind when it solves an unsolved mathematical/physics/scientific problem, i.e: "AI, give me a proof for (or against) the Riemann hypothesis"